Evaluation of laboratory methods to improve characterization of dogs with von Willebrand disease.

The objective of the study was to investigate the value of additional tests [platelet count, partial thromboplastin time (PTT), platelet function analysis using the PFA-100, Collagen binding assay (vWF:CBA), and Factor VIII activity], for use in conjunction with the von Willebrand factor antigen enzyme-linked immunosorbent assay (ELISA), as part of a newly developed diagnostic profile for improved characterization of patients with von Willebrand disease (vWD). The study population included 183 clinically healthy canines ranging in vWF:Ag concentration from 1% to 125%. The Asserachrom vWF:Ag ELISA assay was used as an external control for the determination of vWD status. Degree of association between the additional tests and vWF concentration was evaluated, and associations between the additional tests were also assessed, including their ability to distinguish dogs with vWD from those without vWD. In addition, a reference interval was determined for the PFA-100 platelet function analyzer. Strong associations were found between the PFA-100, vWF:CBA, and Asserachrom vWF:Ag assay, and a significant association was found between the PFA-100 and vWF:CBA. An association was detected between Factor VIII activity and the Asserachrom vWF:Ag assay, the vWF:CBA and the PFA-100; however, a corresponding pattern was not visually apparent in the raw data, making the association clinically irrelevant. The association between the platelet count and the PTT with the other additional tests was negligible. Based on our results, the vWF:CBA and PFA-100 would be valuable assets, in conjunction with a vWF:Ag assay, in a canine vWD diagnostic profile to further characterize patients with this disease.